Various triazine-based herbicides have heretofore been known. For example, 2-methylthio-4,6-bis(alkylamino)-s-triazine derivatives are known to be effective herbicides having a high weed control activity. However, the effect of 2-methylthio-4,6-bis(ethylamino)-s-triazine, for example, greatly varies with conditions such as the type of soil and temperature. In more detail, when used in a mild district, it causes phytotoxicity (injury) even in the commonly used amount, and in a cold district, its effect is exhibited only insufficiently. Thus 2-methylthio-4,6-bis(ethylamino)-s-triazine has a disadvantage in that it can be applied as a herbicide only in a limited district.
The present invention is intended to overcome the above problems and an object of the present invention is to provide a process for preparing a novel herbicide which can exhibit its herbicidal activity nearly equal under various soil and temperature conditions, and also can exhibit its herbicidal activity against various annual weeds and perennial weeds while causing no injury against paddy rice plants and furthermore causing no injury against upland field crops such as corn, oats, wheat, barley and grain sorghum.
As a result of extensive investigations, it has been found that the above objects can be attained by using specified triazine derivatives having a benzofuranyl or thianaphthenyl group, or a dihydrobenzofuranyl or dihydrothianaphthenyl group.